First to address the question someone ask "Are you sure you are paying for HD"
I seem to recall Dish adds. HD is free for life. so yes you are.
Second: Dish recently changed their Sat ID codes, so some older antennas can not lock on. I do not think the Tailgater (Which I believe is made by King Controls) is one of those which can not lock on but my decade old unit can not (Different company) but then it never did the Dish HD.
Dish used 3 sats for transmission, one is HD and it's farther west, if you are in the east odds are you can not see this satellite as it is below the horizion, if this is the case only switching to the eastern arc will help. OF all the antennas out that limits you to the Winegard Pathfinder X-2 (the X1 can not do the eastern arc, neigher can the King Controls made units).
Or a hard dish. I do recommend a Dish-1000.x antenna, but that's my suggestion.